Thermal printing devices are well known in the art. One of the primary applications of thermal printing devices is label making, in which thermal ink is transferred onto a media, like a label, by sending data to the thermal print head and then powering/heating the elements of the thermal print head to transfer the desired pattern of thermal ink onto the label.
FIGS. 1A, 1B, and 1C illustrate a thermal printing system 100 as understood in the art. As shown in FIG. 1A, rolled materials (ribbon 101 and label 102) are unwound (ribbon unwind roll 103 and label unwind roll 104, respectively) and fed through the thermal print head 105 and the pressure roller 106. The elements of the thermal print head 105 are heated to transfer the desired pattern of thermal ink from the ribbon 101 to the label 102. The label 102 is then ejected from the thermal printing device (to be used for the purpose for which it was generated) and the used portion of ribbon 101 is wound up in the ribbon uptake roll 107. As shown in FIG. 1B, the ribbon unwind roll 103 has a ribbon core 108 which rotates around the ribbon unwind spindle 109 to allow the ribbon 101 to be fed into the thermal printing device. Similarly, as shown in FIG. 1C, the label unwind roll 104 has a label core 110 which rotates around the label unwind spindle 111 to allow the label 102 to be fed into the thermal printing device.
As FIGS. 1A, 1B, and 1C illustrate, much of the accuracy with thermal printing stems from the handling of rolled materials. Clearly, if the unwind spindles (109, 111) flex too much during the print job, the printing can warp and become unusable. Similarly, if the tolerance between the cores (108, 110) is too great, then it is possible for the rolled material to slip, which can also warp the printing and render the final product unusable.
Further, many thermal printing devices can be very small (such as barcode label makers, etc.) and have small spindles (such as a 0.5″ diameter spindle). As such, there is not much room in the spindles for the rolled materials that would allow for complex mechanisms to prevent flexing of the spindle and slipping of the core around the spindle.
Accordingly, there is a need for a rigid yet flexible spindle for rolled material in a thermal printing device.